Current research on operant choice (which uses both humans and nonhumans as subjects) is here related to current research on human decision. The bridge between the two spheres of research is a translation of the concept of probability of outcome (directly experienced or verbally expressed) into operant terms--delay of reinforcement or punishment (as schedules or as discriminative stimuli for schedules). A consequence of this translation is that inconsistencies of choice (as expressed by failure of behavior to conform to the axioms of probability theory) may be viewed in terms of self control or its lack (where lack of self control, in turn, is a failure to choose a delayed but larger reinforcer over an immediate but smaller one). (A further analogy to be explored is that between probabilistic and delay discounting on the one hand and social discounting on the other; where social discounting is defined as the degree of selfishness exhibited in a one-versus-many version of a prisoner's dilemma game.) Because much disfunctional human behavior, including smoking, overeating, alcoholism, drug abuse, and unsafe sexual practice, may be seen as failure of self control, the proposed research is directly relevant to mental and physical health.